Spencer Davenport and his sister Katherine must fly from California to Pennsylvania on Christmas Eve to spend the holidays with their dad, an environmentalist. During their layover at the Hoover International Airport in Washington DC, a massive blizzard grounds all planes and cancels all flights, and the siblings are sent to the anarchic UM (Unaccompanied minor passenger) room, where they meet Christmas-spirited smarty-pants Charlie Goldfinch, surly tomboy Donna Malone, arrogant rich girl Grace Conrad, and mysterious Beef Wellington.